With arrival of spring the nature wakes up and then in light and clean reservoirs freshwater hydras are born. These small predators, despite the simple building, on the are unique. Abilities of their body are attentively studied by biologists. One of interesting functions of an organism of a hydra is ability to regeneration, that is restoration of the damaged cages.
Among seaweed in the silent and transparent water environment of lakes, ponds and ditches there lives the tiny predator – a hydra freshwater. It is considered a polyp that in translation means – multilegs. This term is used in zoology and designate by it the inactive or attached to something individuals equipped with tentacles.
As the hydra looks
Freshwater polyp the hydra is a bright representative of coelenterates of animals. The little body at this small almost transparent being has a cylinder appearance. On the one hand at a hydra it is possible to see an oral opening which is supplied with thin tentacles. Their quantity can be a miscellaneous, as a rule, from 5 to 12 pieces. On other part the small stalk and a sole which is necessary for sticking to seaweed, sticks and pebbles is located. The general size of a predator is equal to 5 - 7 mm, at the same time tentacles at it long. They are able to stretch for several centimeters.
What means the term beam symmetry
Concept the beam symmetry means special arrangement of parts of a body at some representatives of fauna. If to assume that along all body the imagined axis is laid, then tentacles at a hydra will begin to disperse like beams of the sun in different directions from an axis. For hunting for little crustaceans, a predator it is stuck to seaweed or stones under water. It is shaken on a subject, and radial tentacles waiting for the victim move to the different directions.
As the body of a hydra is arranged
The type of coelenterates of animals, including a hydra, possesses the only cavity - intestinal. Therefore the little body reminds a sack which walls contain 2 layers of cages, forming an outer layer and an inside layer.
Outer layer
If attentively to consider this layer, using a microscope, then it will be well visible that it is possible to find different cages in it. The basis of a layer is represented by skin and muscular cages. From them the external cover of a little body turns out. Each cage is supplied with a muscular fibril, with its help the hydra has an opportunity to move. When there is a reduction of skin and muscular cages, the hydra little body contracts at once. For a body tilt, cages have to be reduced from outside in which the inclination will be carried out. Stepping on a surface a leg, the hydra turns over and gets up on the tentacles. Somersaulting, it moves in objects.
Except skin and muscular cages in an outer layer it is possible to find neurons, similar to stars. They are equipped with axons which touch muscular cages. At contact among themselves axons form a nervous texture.
Reaction to irritation
The freshwater hydra perfectly feels touches, reacts to changes of temperature and also to other irritants which surround it. If to concern a hydra little body, then she will contract. The impulse from an irritant passes through the nervous terminations and gets into skin and muscular cages. Muscular fibrils are reduced at once, and the little body sharply contracts in a tiny lump. As the organism of a polyp is arranged primitively, and reflexes at it same.
For what strekatelny cages are necessary
To get food the hydra has strekatelny cages, important for hunting. They are placed on all little body, including tentacles. Such cage has the difficult device. In it there is a special capsule in which the strekatelny (stinging) thread is laid. To a surface a cage there is a special touch hair.
At contact of a hair with an irritant, for example a crustacean, strekatelny thread is immediately straightened and stings production. From the capsule poison which kills her gets into the victim. When the crustacean is killed, tentacles of a predator accurately take food and send it to an oral opening.
Production of food not the only function of strekatelny cages. They protect a polyp from other inhabitants of a reservoir. Poison of a hydra has the effect similar to a burn on fish and other larger individuals a nettle.
As internal cages are arranged
The cages which are in an inside layer consist of special muscular fibers. They are necessary to a polyp for digestion. Cages produce digestive juice which helps food to decay quickly on small particles. Some cages are supplied with special zhgutika. They catch crumbs of food and pull towards a cage. Particles are able to capture Lozhnonozhki which equipped cages, and further digestion happens in special vacuoles which are placed in a cage. Not the necessary remains of food are evacuated outside directly through a mouth.
The hydra has no respiratory system. The oxygen dissolved in water freely passes through cells of a body of an underwater being. Therefore breath of a hydra is carried out by a little body.
Ability to regeneration
In cages of an outer layer of a cover of a freshwater hydra there are special roundish cages. In them there are especially large kernels. These are intermediate cages, they are necessary for healing of damages on a body.
At violation of a cover, at a wound intermediate cages quickly begin to accrue. As a result they reproduce the destroyed skin and muscular and nervous fibers that promotes the fastest healing of a wound.
The ability to fast cell regeneration at a freshwater polyp is expressed much more brightly, than at other animals. If to divide his body across, then 2 new hydras will grow from two parts. In that half where there was a sole, there will be tentacles and a mouth, and other half on which there were tentacles, will recreate a new sole and a small stalk.
The restoration processes happening in a body of a hydra are attentively studied by biologists. Understanding of these processes gives the chance to develop methods for treatment of wounds at people.
Ways of reproduction of a freshwater hydra
The freshwater hydra is able to propagate in two ways. Depending on conditions and season the reproduction can be made sexually or sexless.
Sexless option of reproduction
This option is called budding. Polyps use sexless process only in good conditions, as a rule, in warm season. On a body of an adult individual there is in the beginning a small protrusion which then develops into a hillock. Gradually it increases in sizes, is extended in length and on it tentacles begin to grow, then the mouth appears. After a while the young hydra separates from a maternal body and begins independent life. Asexual reproduction reminds life of plants when from a kidney the new escape grows. Therefore this process is also called budding.
Sexual reproduction
When the summer comes to an end, freshwater polyps begin to die. Before the hydra dies, in her organism gametes begin to develop. They can be both men's (spermatozoa), and women's (egg cages). Spermatozoa are equipped with a special zhgutik which allows them to float freely under water. After an exit from a hydra organism they reach an individual with an egg cage.
Having got in such hydra, the spermatozoon connects to an egg cage, their kernels unite, and there is a fertilization process. Then this new cage becomes roundish, its lozhnonozhka clean up inside, and the strong outer sheath from above accrues. As a result of these actions, egg is formed.
Late fall of a hydra will die, and their eggs will survive and will fall to a lake bottom. There they will winter. In the spring when there come suitable conditions, in the section which remained under a protective strong cover of egg there is a division process. New cages quickly grow, forming two layers. Finally the young hydra who breaks through a protective cover and comes up from it in water is born.